Ok, not strictly linux only: I use F18/Cinnamon/Firefox19.0.2 or Windows 7/FF version unknown. I have noticed that the same feature is enabled in seamonkey also so it is looking like a website feature.
I go to one of the forum pages on LQ (or fedoraforum.net) and begin to browse. Wherever my mouse sits it brings up a preview pane showing a description of that thread. If I want to look at the specific thread then that could be helpful. As it is, I am browsing the headings for each post and the pane is quite irritating and not required.
I'll point out that one of the other forums I browse
http://forums.whirlpool.net.au/forum/39 does not have this feature.
If the description above is sufficient, is there any way of controlling this feature?
Cheers